I'll take a shot at the logic (pun intended), for keeping guns out of bars, regardless of a license. The belief, as silly as it is, is that alcohol, which is served at bars, among other places, can hinder a normal person's self control (I have never seen this before (*rolling eyes* while thinking back to Pat O'Briens' in New Orleans twenty years ago)); therefore, if a non-criminal is carrying a gun, it is possible for the person to lose self control, after alcohol consumption at the bar, and shoot something or someone.
Applied to Doug's logic, there is an opportunity for a greater number of people to lose self control and shoot something or someone.
I'm sure some people believe there is an opportunity for a greater number of people to have self control and apply their control to the criminal who is not exhibiting self control.